In recent years, a vehicle switch mounted on the dashboard or near the steering wheel in the interior of the car has gained popularity because it is convenient for the driver to operate a variety of electronic devices such as an audio system or an air-conditioner. The vehicle switch is thus required to be easy to operate and to perform its function reliably.
A conventional vehicle switch disclosed in Unexamined Japanese Patent Application Publication No. 2003-308759 (Patent Document 1) is described hereinafter with reference to FIGS. 13-16. FIG. 13 shows a sectional view of the conventional vehicle switch, and FIG. 14 shows an exploded perspective view of this conventional vehicle switch. In FIGS. 13 and 14, vehicle switch 11 comprises the following elements:
a disk-like wiring board 1 made of insulating resin; and
encoder 2 working as a switch contact of a rotary-switch and placed approximately at the center of wiring board 1.
Multiple wiring patterns (not shown) are formed on both the faces of wiring board 1. Push switch 3 working as a switch contact of a push-switch is mounted in hollow cylinder 2A of encoder 2.
Operating unit 4 shaped like a cylinder with an opening at its center and made of insulating resin is mounted to rotary operating section 2B formed on an upper section of encoder 2. Push button 5 shaped like a cylinder and made of insulating resin is accommodated in the opening of operating unit 4 such that it can move up and down.
As discussed above, various electronic components such as encoder 2 and push switch 3 are mounted on wiring board 1. Switch unit 10 is thus formed of wiring board 1, encoder 2, push-switch 3, operating unit 4, and push button 5. A rotation of operating unit 4 prompts encoder 2 to perform an electrical switch-on or switch-off. A push onto push button 5 depresses push-switch 3 via pressing section 5A, whereby push-switch 3 performs an electrical switch-on or switch-off.
Housing 6 shaped like a cylindrical box with a bottom plate and made of insulating resin includes multiple fixing sections 6A at its inner wall, and each one of fixing sections 6A protrudes inward. Wiring board 1 of switch unit 10 is placed on fixing sections 6A. Wiring board 1 has multiple cutouts 1A corresponding to fixing sections 6A, and is screwed to fixing sections 6A with screws 7, so that switch unit 10 is fixed to housing 6. Operating unit 4 placed on housing 6 is covered with cylindrical cover 8 at its outer wall, and cover 8 is mounted on the top face of housing 6, whereby vehicle switch 11 is constructed.
The foregoing vehicle switch 11 is mounted on the dashboard or near the steering wheel in the car interior with operating unit 4 protruding forward. When operating unit 4 is operated by a driver, encoder 2 or push-switch 3 is connected electrically to an electronic circuit (not shown) of the car via the wiring patterns, switch contacts, connectors and lead wires (not shown) of wiring board 1.
A downward push onto push-button 5 with a finger lowers push-button 5, and a lower end of pressing section 5A depresses push-switch 3, so that push-switch 3 can perform an electrical switch-on or switch-off. An electrical signal generated by this switch-on or switch-off is supplied to the electronic circuit of the car, thereby turning on or off the power supply of, e.g. the audio system or the air-conditioner.
When the operating unit 4 protruding upward from cover 8 is held with fingers, and rotated, rotating section 2B of encoder 2 rotates in synchronization with the rotation of operating unit 4. An electrical switch-on or switch-off of the inner switch contact is repeated in response to a rotation amount of rotating section 2B, and an electrical signal generated by this switch-on or switch-off is supplied to the electronic circuit of the car, thereby increasing or decreasing a sound volume of the audio system or a temperature of the air-conditioner.
Operating unit 4 generally protrudes from the top face of cover 8 by 20-30 mm to be held and rotated easily with fingers. Baggage in the car interior sometimes hits this protrusion, so that a large load or shock is applied to operating unit 4 or push-button 5, thereby damaging encoder 2, push-switch 3 or wiring board 1. Switch unit 10 as a whole thus sometimes subsides into housing 6.
Problems of the conventional vehicle switch are described hereinafter with reference to FIG. 13 and FIG. 15A-FIG. 16B. FIGS. 15A and 15B show sectional views illustrating the operation of the conventional vehicle switch. FIG. 15B shows a status where a greater load or shock is applied to operating unit 4 or push-button 5 than a load or a shock applied to them shown in FIG. 15A. FIGS. 16A and 16B show perspective views illustrating the operation of the conventional vehicle switch. FIG. 16A shows a normal status, and FIG. 16B shows the status where a greater load or shock is applied to operating unit 4 or push-button 5 than a load or a shock applied to them in the normal status shown in FIG. 16A. To be more specific, when baggage in a car interior hits operating unit 4 or push button 5, and a large load or shock is applied to operating unit 4 or push button 5, then the normal status shown in FIG. 13 or FIG. 16A changes to the status shown in FIG. 15A, where crack 1D occurs on wiring board 1. Encoder 2 or push-switch 3 can be cracked depending on the magnitude or the direction of the load or the shock. When the greater load or shock than the foregoing case is applied to operating unit 4 or push button 5, wiring board 1 is broken near fixing section 6A of housing 6, and then as shown in FIG. 15B and FIG. 16B, switch unit 10 as a whole sometimes subsides into housing 6.
A user can operate various devices installed in the car interior by rotating operating unit 4 or pressing push button 5 of vehicle switch 11 mounted on the dashboard or near the steering wheel of the car. However, when a large load or shock is applied to operating unit 4 or push button 5, encoder 2 or push switch 3 of switch unit 10, or wiring board 1 including switch contacts tends to be broken.